Osteochondritis dissecans is a condition wherein a small fragment of bone becomes separated from one of the femoral condyles. The usual treatment is debridement and drilling, followed by insertion of a fixation device. Commonly used fixation devices include wires, screws, nails and pins.
The conventional treatment techniques suffer from a number of drawbacks and limitations. For example, wires do not form a secure fixation of the fragment to the femoral condyle and, in addition, a wire may protrude from the fragment. Should the knee be moved while the wire is protruding, then the proximal tibia of the knee joint may be gouged.
Screws have also been used to internally fix the fragment to the femoral condyle, but screws likewise suffer from drawbacks. The typical bone screw has a cruciate head providing an irregular, interrupted surface facing the tibial plateau. As a result, movement of the knee may cause gouging of the tibial plateau as the interrupted area is engaged.
Regardless of the fixation device utilized, it is advantageous that the device be secured in a fixation assembly permitting manipulation of the fragment, and insertion and withdrawal of the fixation device, all with relative ease. There has been a tendency for insertion of the fixation device to be performed anthroscopially, thereby presenting a relatively small portal for the entrance of the fixation device and fixation device holder.
Those skilled in the art will appreciate that there is a need for a bone screw which may be readily installed for securely fixing the bone fragment to the femoral condyle, while also minimizing the possibility of the proximal tibia becoming gouged during movement of the joint. There is likewise a need for a bone screw holder which is easy to manipulate, which securely grasps the bone screw in order to facilitate manipulation of the fragment and insertion of the screw, and which readily seizes the bone screw in order to permit its removal after the treatment is completed. The disclosed invention is just such a bone screw and bone screw holder.